The purpose of this research is: 1. To determine if human lymphocytes can react in vitro to tumor associated antigens or intact tumor cells from an autochthonous or allogenic source with proliferation and the production of interferon, a mediator of cellular immunity. 2. To determine the role of human macrophages from tumor bearing patients in this reaction. 3. To determine the effect of normal human sera, fetal calf serum, and sera from tumor bearing patients on this reaction. 4. To determine if the extent of interferon production is a function of the nature of the tumor, severity or stage of the disease, or the therapy administered.